The present invention relates to a gas-insulated switchgear and, more particularly, to a gas-insulated switchgear for which a constitution of a composite gas-insulated switchgear is improved.
A composite gas-insulated switchgear with an increasing production lately is constituted generally as shown in FIG. 1. In the drawing, 1 denotes a breaker enclosing a breaking unit together with SF.sub.6 gas in a grounded horizontal tank, 2 denotes an air bushing, which is placed on one end of the breaker at one terminal part of the switchgear. It is also placed on a tank of a disconnector 3 provided on the other end of the breaker 1 at the other terminal part. The terminal part of each air bushing 2 is connected to an air bus part insulated atmospherically or a lead for line circuit. One terminal part 4 of the disconnector 3 and a terminal part 4a of the breaker 1 are connected through a window type current transformer 5 intermediately. A terminal part 8 of a grounding switch 7 is provided on a terminal part 6 connected to the bushing 2 of the disconnector 3. Then, a lightning arrester 9 is provided for coordination of insulation between the gas-insulated switchgear and a lightning surge, a terminal part 9a of the lightning arrester 9 is connected to the terminal part 6 of the disconnector 3 with a conductor 10, and an electrostatic capacity type of intermediate electrode 11 to detect a voltage on the line side by means of said conductor 10 is arranged cylindrically as coaxial with the conductor 10.
In such constitution, since the grounding switch 7 is arranged on a portion coming comparatively upper at the disconnector 3, its operation involves a producing of various metal powders through sliding, and such powders drop into the tank of the disconnector 3 and thus come to deposit on an insulating spacer 12 to support the one terminal part 4 of the disconnector 3. The situation that the metal powders stick to the insulating spacer 12 may invite a deterioration, after all, in insulating performance of the gas-insulated switchgear. Particularly of late, a large scale and large capacity transmission (550 KV/12 KA transmission line being 200 km or longer) is being realized, a switching duty of a grounding switch used for the gas-insulated switchgear to be employed for such transmission system becomes severe as compared with that of conventional one accordingly, and the situation is such that a 90 KV/1,500 A induced current breaking is required as an example for the switching ability. To allow the grounding switch to operate in such switching ability, a gas spray function, i.e. puffer spray will be employed on the contact part. However, a large switching mechanism 13 will have to be provided to enclose such grounding switch 7 in the tank of the disconnector 3, which may involve a hardship in consequence. Moreover, the quantity of dusts produced at the time of induced current breaking will increase inevitably to deposit on the insulating spacer 12, which deteriorates a dielectric strength of the insulating spacer 12, therefore an employment of a pollution-proof insulating spacer with a long creeping distance or a spacer somewhat larger in size will have to be taken into consideration. Then, the grounding switch 7 is mounted comparatively at high position, and hence a special operating floor must be prepared for operation and inspection.